The invention relates to polymeric compositions, particularly polyurethanes, which are producible using a mixture of two or more polyols, a process for manufacturing such compositions as well as the use of such compositions.
Polyurethanes, particularly due to their use in surface coating agents, adhesives and in sealing technology, have become versatile plastics that can be used in many technological areas. Those polyurethanes comprising reactive end groups that can be crosslinked by means of an externally added compound are of particular interest. Examples of such end groups are those that can react with water, for example in the form of humid air.
This type of reactivity allows the reactive polyurethanes to be brought in a processable state to the required place and cured by the action of humid air or the like with the reactive end group compounds. Generally, the curing agent is added prior to processing, with the result that after the addition of the curing agent, there remains only a limited processing time available to the processor.
Exemplary reactive end groups include isocyanate end groups. Polyurethanes with such end groups already cure with suitable functionality under the influence of air humidity. However, in the presence of water, for example, the use of polyurethanes comprising NCO end groups can give rise to the formation of carbon dioxide. Whereas this generally does not cause a problem, for some applications, however, the generation of carbon dioxide has adverse effects on the surface structure. Moreover, such polyurethanes will often not adhere to smooth, inert surfaces, for example on glass, ceramic, metal surfaces and the like.
To redress this, i.e. in order to permit a strong and permanent bond of polyurethanes with the abovementioned surfaces, in such cases it has been proposed in the prior art to introduce, for example, an alkoxy silane as the reactive end group into the polyurethane.
Over the last years, polymers carrying silyl groups in particular have become increasingly important as binders for adhesives, sealants and foams. These polymers are generally polyurethane prepolymers comprising alkoxysilane end groups. However, other solutions to the above problems have been suggested in the prior art.
Thus, a curable polymer based on an acrylic and/or methacrylic acid ester and a curable oxyalkylene polymer has been described, for example in EP 0 265 929 B1. In particular, a curable compound is described comprising                (a) a copolymer that comprises silicon-containing functional groups capable of being crosslinked through the formation of siloxane bonds and whose molecular chain consists of 50 wt. % or more of                    (1) an alkyl acrylate ester monomer unit and/or an alkyl methacrylate ester monomer unit that each have an alkyl group of 1 to 8 carbon atoms, and            (2) an alkyl acrylate ester monomer unit and/or an alkyl methacrylate ester monomer unit that each have an alkyl group of at least 10 carbon atoms.                        (b) an oxyalkylene polymer comprising silicon-containing functional groups capable of being crosslinked through the formation of siloxane bonds; and        (c) a curing accelerator.        
Generally, solvent-based elastic adhesives are easy to handle. However, such elastic adhesives possess essential ingredients that are environmentally toxic and moreover are inflammable. Numerous attempts have been made to overcome these disadvantages. For example, alternatives such as solvent-free adhesives and aqueous contact adhesives have been developed.
A moisture curable composition that is suitable as an adhesive is described in U.S. Pat. No. 6,306,966 B1. The composition is produced by mixing a component A comprising.                (i) monomer units of alkyl acrylate- and/or alkyl methacrylate carrying silyl groups with an alkyl group containing 1 to 8 carbon atoms and        (ii) monomer units of alkyl acrylate- and/or alkyl methacrylate carrying silyl groups with an alkyl group containing 10 or more carbon atoms and        (iii) an oxyalkylene polymer with reactive Si groups        with a component B that comprises an amorphous powder having a particle size of 0.01 to 300 μm.        
However, the above-described systems have a disadvantage in that in many cases the tensile strengths obtained with such compositions are borderline. Moreover, the effort required to incorporate polymers into the strength-giving structure of an adhesive is often laborious.
Thus, the object of the present invention is to provide compositions that do not exhibit the above-described disadvantages. In particular, an object of the present invention is to provide compositions that exhibit a high tensile strength. A further object of the present invention is to provide a manufacturing process for the inventive compositions.
It has now been discovered that compositions, particularly polyurethanes that are manufactured using a mixture of two or more polyols, do not exhibit the above-described disadvantages of the prior art. Concerning the inventive finding, it is particularly surprising that the used mixture of two or more polyols according to the invention is universally suited to impart a markedly improved tensile strength in the crosslinked state to crosslinking compositions, in particular based on crosslinked silyl groups or isocyanate groups.